AAP

The realisation of the long-awaited National Disability Insurance Scheme (NDIS) has been widely welcomed, although questions have been raised about how it will be funded.

The scheme, proposed by the Productivity Commission, will cover many of the costs of people born with disabilities or who become incapacitated later in life.

At a rally in Sydney on Monday, Prime Minister Julia Gillard announced funding would be set aside in next week's budget to launch the NDIS but she wouldn't say how much.

"People with disabilities have waited a long time for change," Ms Gillard said.

"We will be working with states and territories to get this done."

The announcement was made at the NDIS Make it Real rally of almost 2000 people at Sydney Olympic Park, with similar events held across Australia.

From the middle of next year, select launch sites will begin serving 10,000 people with a disability - "a full year sooner than the Productivity Commission suggested", Ms Gillard said.

By mid-2014, about 20,000 people will have been served.

However, shadow treasurer Joe Hockey said Ms Gillard had to explain how the government was funding the scheme.

"The NDIS is a very worthy scheme, but it sounds to me like the dying days of a government, where they make big heroic announcements about massive programs and they won't tell you how they pay for it," Mr Hockey told reporters in Sydney.

He estimated the scheme would cost $8 billion a year.

"That's the equivalent of roughly increasing the Medicare levy by one per cent," he said.

Addressing a Perth rally, federal Opposition Leader Tony Abbott said he offered the government bipartisan support.

"I offer the government bipartisan support for a responsible and timely NDIS," Mr Abbott told the 500-strong crowd who had turned up in support of the NDIS.

"And I think the best way forward ... is to have a bipartisan parliamentary committee, chaired by both sides' disabilities frontbenchers, to ensure that it gets looked after at a political level."

"That will be very hard for a lot of Australian families to pay."

In Sydney, NSW Premier Barry O'Farrell, who also attended the rally, said people with a disability and their carers shouldn't have to rally to get what should be theirs by right.

"The NSW government is prepared to work with the federal government to make NDIS a reality," Mr O'Farrell told the gathering.

ACTU president Ged Kearney said the NDIS was a major social reform akin to the introduction of Medicare.

"Proper funding will transform the system with greater pay, more jobs, better working conditions and career structures, and the resources to do the job properly," Ms Kearney said.

United Voice, the disability workers' union, said it was significant step towards improving the long-neglected disability sector.